Abstracts
Reliability is essential to all aspects of the measure, as it shows the quality of the information and allows rational conclusions with regard to the data. There has been controversial results regarding the reliability of electromyographic parameters assessed during stair ascent and descent in individuals with patellofemoral pain syndrome (PFPS). Therefore, this study aims to determine the reliability of time and frequency domain electromyographic parameters on both gestures in women with PFPS. Thirty-one women with PFPS were selected to participate in this study. Data from vastus lateralis and medialis were collected during stair deambulation. The selected parameters were: automatic onset, median frequency bands of low, medium and high frequency. Reliability was determined by intraclass correlation coefficient and the standard error of measurement. The frequency domain variables have shown good reliability, with the stair ascent presenting the best rates. On the other hand, onset has proved to be inconsistent in all measures. Our findings suggest that stair ascent is more reliable than stair descent to evaluate subjects with PFPS in the most cases.
electromyography; reproducibility of results; patellofemoral pain syndrome
A reprodutibilidade é essencial para todos os aspectos da medida, uma vez que mostra a qualidade da informação e permite conclusões racionais no que diz respeito aos dados. Além disso, os resultados são controversos sobre parâmetros eletromiográficos avaliados durante a subida e descida de escada em indivíduos com síndrome da dor femoropatelar (SDFP). Portanto pretende-se determinar a reprodutibilidade de parâmetros eletromiográficos nos domínios do tempo e da frequência em ambos os gestos em mulheres com SDFP. Foram selecionadas 31 mulheres com SDFP. Os dados dos músculos vasto lateral e vasto medial foram coletados durante a subida e a descida de escada. Os parâmetros selecionados foram: o onset automático, frequência mediana, bandas de baixa, média e alta frequência. Determinou-se a reprodutibilidade através do coeficiente de correlação intraclasse e do erro padrão da medida. As variáveis no domínio da frequência apresentaram boa reprodutibilidade, com a subida apresentando os melhores índices, e o onset mostrou-se inconsistente. Os resultados sugerem que a subida de escada é mais confiável do que a descida da escada para avaliar indivíduos com SDPF na maioria dos casos.
eletromiografia; reprodutibilidade dos testes; síndrome da dor patelofemoral
La reproducibilidad es esencial para todos los aspectos de la medida, ya que muestra la calidad de la información y permite conclusiones racionales con respecto a los datos. Además, los resultados son controvertidos en parámetros electromiográficos evaluados durante el ascenso y descenso escaleras en las personas con síndrome de dolor patelofemoral (SDPF). Por eso tenemos la intención de determinar la reproducibilidad de los parámetros electromiográficos en el tiempo y la frecuencia en ambos gestos en mujeres con SDPF. 31 mujeres com SDPF fueron seleccionadas. Se recogieron datos del vasto lateral y medial durante ascenso y descenso de escaleras. Los parámetros seleccionados fueron: inicio automático, frecuencia mediana, bandas de baja, media y alta frecuencia. La reproducibilidad se determinó mediante el coeficiente de correlación intraclase y el error estándar de medición. Las variables en el dominio de la frecuencia mostraron buena reproducibilidad, el ascenso presentó lós mejores índices, y el inicio demostró ser inconsistente. Estos resultados sugieren que el ascenso de la escalera es más confiable que el descenso para evaluar individuos con SDPF en la mayoría de los casos.
electromiografía; reproducibilidad de resultados; síndrome de dolor patelofemoral
Introduction
Patellofemoral pain syndrome (PFPS) has been responsible for 25 to 40% of all knee
problems registered in orthopedic centers (Boling
et al., 2010Boling, M., Padua, D., Marshall, S., Guskiewicz, K., Pyne, S., &
Beutler, A. (2010). Gender differences in the incidence and prevalence of
patellofemoral pain syndrome. Scandinavian Journal of Medicine & Science in
Sports, 20, 725-730. doi:10.1111/j.1600-0838.2009.00996.x.Gender
https://doi.org/10.1111/j.1600-0838.2009...
). It is a condition characterized by
non-specific anterior knee pain, with an insidious onset(Grenholm, Stensdotter, & Häger-Ross, 2009Grenholm, A., Stensdotter, A.-K., & Häger-Ross, C. (2009). Kinematic
analyses during stair descent in young women with patellofemoral pain. Clinical
Biomechanics, 24, 88-94. doi:10.1016/j.clinbiomech.2008.09.004
https://doi.org/10.1016/j.clinbiomech.20...
). Different daily activities
such as, ascending and descending stairs, squatting and running, have been pointed as a
potential exacerbating factor(de Oliveira Silva
et al., 2015De Oliveira Silva, D., Briani, R.V., Pazzinatto, M.F., Ferrari, D.,
Aragão, F.A., de Albuquerque, C.E., ... de Azevedo, F.M. (2015). Reliability and
differentiation capability of dynamic and static kinematic measurements of rearfoot
eversion in patellofemoral pain. Clinical Biomechanics, 30, 144-148.
doi:10.1016/j.clinbiomech.2014.12.009
https://doi.org/10.1016/j.clinbiomech.20...
; Willson,
Sharpee, Meardon, & Kernozek, 2014Willson, J.D., Sharpee, R., Meardon, S.A., & Kernozek, T.W. (2014).
Effects of step length on patellofemoral joint stress in female runners with and
without patellofemoral pain. Clinical Biomechanics, 29, 243-247.
doi:10.1016/j.clinbiomech.2013.12.016
https://doi.org/10.1016/j.clinbiomech.20...
).
Stair ascent or descent is a cheap and simple way to simulate a daily life activity in a
laboratory environment(Garcia et al.,
2010Garcia, F.R., Azevedo, F.M., Alves, N., Carvalho, A.C., Padovani, C.R.,
& Negrão Filho, R.F. (2010). Effects of electrical stimulation of vastus medialis
obliquus muscle in patients with patellofemoral pain syndrome: an electromyographic
analysis. Revista Brasileira de Fisioterapia, 14, 477-82. (Retrieved from
http://www.ncbi.nlm.nih.gov/pubmed/21340241)
http://www.ncbi.nlm.nih.gov/pubmed/21340...
; Riener, Rabuffetti, & Frigo,
2002Riener, R., Rabuffetti, M., & Frigo, C. (2002). Stair ascent and
descent at different inclinations. Gait & Posture, 15, 32-44.). As stair deambulation is often used to evaluate the reproducibility of
symptoms and to identify abnormal movement patterns indicative of PFPS, knowledge of
lower extremity neuromuscular activity during stair deambulation is necessary to better
characterize compensatory behaviors in this population(Salsich, Brechter, & Powers, 2001Salsich, G.B., Brechter, J.H., & Powers, C.M. (2001). Lower
extremity kinetics during stair ambulation in patients with and without
patellofemoral pain. Clinical Biomechanics, 16, 906-912.
doi:10.1016/S0268-0033(01)00085-7
https://doi.org/10.1016/S0268-0033(01)00...
). The electromyography (EMG) parameters
have been frequently investigated in PFPS studies during stair descent (Herrington, Malloy, & Richards, 2005Herrington, L., Malloy, S., & Richards, J. (2005). The effect of
patella taping on vastus medialis oblique and vastus laterialis EMG activity and knee
kinematic variables during stair descent. Journal of Electromyography and
Kinesiology, 15, 604-7. doi:10.1016/j.jelekin.2005.05.002
https://doi.org/10.1016/j.jelekin.2005.0...
; Saywell, Taylor, & Boocock, 2012Saywell, N., Taylor, D., & Boocock, M. (2012). During step descent,
older adults exhibit decreased knee range of motion and increased vastus lateralis
muscle activity. Gait & Posture, 36, 490-4.
doi:10.1016/j.gaitpost.2012.05.007) and stair
ascent (Kuriki, De Azevedo, Filho, & Alves,
2012Kuriki, H.U., De Azevedo, F.M., Filho, R. de F.N., & Alves, N.
(2012). Onset of quadriceps activation and torque variation during stair ascent in
individuals with patellofemoral pain. Conscientiae Saúde, 11, 642-650.
doi:10.5585/ConsSaude.v11n4.3810
https://doi.org/10.5585/ConsSaude.v11n4....
; Sung & Lee, 2009Sung, P.S., & Lee, D.C. (2009). Gender differences in onset timing
and activation of the muscles of the dominant knee during stair climbing. The Knee,
16, 375-80. doi:10.1016/j.knee.2009.02.003
https://doi.org/10.1016/j.knee.2009.02.0...
), however,
data obtained during one gesture may not be applicable to the other due to different
motor strategies imposed to their realization. For example, the gesture of descent is
more challenging for the neuromuscular coordination system due to the need to generate
eccentric forces to decelerate the movement (Leitner,
Schmid, Hilfiker, & Radlinger, 2011Leitner, M., Schmid, S., Hilfiker, R., & Radlinger, L. (2011).
Test-retest reliability of vertical ground reaction forces during stair climbing in
the elderly population. Gait & Posture, 34, 421-5.
doi:10.1016/j.gaitpost.2011.06.014
https://doi.org/10.1016/j.gaitpost.2011....
). On the other hand, during the
gesture of ascent the quadriceps muscle is more required and the vastus lateralis (VL)
remains active for a longer time compared to the rectus femoris or hamstrings
antagonists(McFadyen & Winter, 1988McFadyen, B.J., & Winter, D.A. (1988). An integrated biomechanical
analysis of normal stair ascent and descent. Journal of Biomechanics, 21, 733-744.
doi:10.1016/0021-9290(88)90282-5
https://doi.org/10.1016/0021-9290(88)902...
).
Therefore, it seems reasonable to investigate the reliability in both gestures and
compare their results to find the better functional activity to study PFPS.
Several studies aim to characterize the activation pattern of the patella stabilizers
muscles during stair deambulation (Cavazzuti, Merlo,
Orlandi, & Campanini, 2010Cavazzuti, L., Merlo, A., Orlandi, F., & Campanini, I. (2010).
Delayed onset of electromyographic activity of vastus medialis obliquus relative to
vastus lateralis in subjects with patellofemoral pain syndrome. Gait & Posture,
32, 290-5. doi:10.1016/j.gaitpost.2010.06.025
https://doi.org/10.1016/j.gaitpost.2010....
; Kim &
Song, 2012Kim, H., & Song, C.H. (2012). Comparison of the VMO/VL EMG Ratio and
Onset Timing of VMO Relative to VL in Subjects with and without Patellofemoral Pain
Syndrome. Journal of Physical Therapy Science, 24, 1315-1317.
doi:10.1589/jpts.24.1315
https://doi.org/10.1589/jpts.24.1315...
), however, few of them present data related to the quality of these
measures (Bolgla, Malone, Umberger, & Uhl,
2010Bolgla, L.A, Malone, T.R., Umberger, B.R., & Uhl, T.L. (2010).
Reliability of electromyographic methods used for assessing hip and knee
neuromuscular activity in females diagnosed with patellofemoral pain syndrome.
Journal of Electromyography and Kinesiology, 20, 142-7.
doi:10.1016/j.jelekin.2008.11.008
https://doi.org/10.1016/j.jelekin.2008.1...
; Cowan, Bennell, & Hodges,
2000Cowan, S.M., Bennell, K.L., & Hodges, P.W. (2000). The test-retest
reliability of the onset of concentric and eccentric vastus medialis obliquus and
vastus lateralis electromyographic activity in a stair stepping task. Physical
Therapy in Sport, 1, 129-136. doi:10.1054/ptsp.2000.0036
https://doi.org/10.1054/ptsp.2000.0036...
; Ferrari, Kuriki, Silva, Alves, &
Mícolis de Azevedo, 2014Ferrari, D., Kuriki, H.U., Silva, C.R., Alves, N., & Mícolis de
Azevedo, F. (2014). Diagnostic Accuracy of the Electromyography Parameters Associated
With Anterior Knee Pain in the Diagnosis of Patellofemoral Pain Syndrome. Archives of
Physical Medicine and Rehabilitation, 95, 1521-6.
doi:10.1016/j.apmr.2014.03.028
https://doi.org/10.1016/j.apmr.2014.03.0...
). Thereby, it is unknown which gesture has the best
results of precision and reliability, yet, whether some specific EMG parameter has
better accuracy depending on the gesture.
The EMG data can be analyzed in two different domains, the time and the frequency domain
(Winter, 2009Winter, D.A. (2009). Biomechanics and motor control of human movement
(Fourth Edi.). New Jersey.). The delay between vastus
medialis (VM) and VL muscle onset is a classical time domain parameter investigated in
individuals with PFPS due to its possible relation to the PFP etiology (Kim & Song, 2012Kim, H., & Song, C.H. (2012). Comparison of the VMO/VL EMG Ratio and
Onset Timing of VMO Relative to VL in Subjects with and without Patellofemoral Pain
Syndrome. Journal of Physical Therapy Science, 24, 1315-1317.
doi:10.1589/jpts.24.1315
https://doi.org/10.1589/jpts.24.1315...
; Pal et al., 2010Pal, S., Draper, C.E., Fredericson, M., Gold, G.E., Delp, S.L., Beaupre,
G.S., & Besier, T.F. (2010). Patellar maltracking correlates with vastus medialis
activation delay in patellofemoral pain patients. The American Journal of Sports
Medicine, 39, 590-8. doi:10.1177/0363546510384233
https://doi.org/10.1177/0363546510384233...
; Patil, Dixon, White, Jones, & Hui, 2011Patil, S., Dixon, J., White, L., Jones, A., & Hui, A. (2011). An
electromyographic exploratory study comparing the difference in the onset of
hamstring and quadriceps contraction in patients with anterior knee pain. The Knee,
18, 329-32. doi:10.1016/j.knee.2010.07.007
https://doi.org/10.1016/j.knee.2010.07.0...
; Uliam Kuriki, Mícolis de Azevedo, de Faria Negrão Filho, & Alves, 2011Uliam Kuriki, H., Mícolis de Azevedo, F., de Faria Negrão Filho, R.,
& Alves, N. (2011). Comparison of different analysis techniques for the
determination of muscle onset in individuals with patellofemoral pain syndrome.
Journal of Electromyography and Kinesiology : Official Journal of the International
Society of Electrophysiological Kinesiology, 21, 982-7.
doi:10.1016/j.jelekin.2011.08.002
https://doi.org/10.1016/j.jelekin.2011.0...
).
On the other hand, frequency domain parameters have been currently used in studies with
PFPS and promising results have been shown (Briani
et al., 2015Briani, R.V., de Oliveira Silva, D., Pazzinatto, M.F., Albuquerque,
C.E., Ferrari, D., Aragão, F.A., & Azevedo, F.M. (2015). Comparison of frequency
and time domain electromyography parameters in women with patellofemoral pain.
Clinical Biomechanics, 30, 302-307.
doi:10.1016/j.clinbiomech.2014.12.014
https://doi.org/10.1016/j.clinbiomech.20...
; Ferrari
et al., 2014Ferrari, D., Kuriki, H.U., Silva, C.R., Alves, N., & Mícolis de
Azevedo, F. (2014). Diagnostic Accuracy of the Electromyography Parameters Associated
With Anterior Knee Pain in the Diagnosis of Patellofemoral Pain Syndrome. Archives of
Physical Medicine and Rehabilitation, 95, 1521-6.
doi:10.1016/j.apmr.2014.03.028
https://doi.org/10.1016/j.apmr.2014.03.0...
). Although some studies have evaluated the
reliability of the electromyography data (Bolgla
et al., 2010Bolgla, L.A, Malone, T.R., Umberger, B.R., & Uhl, T.L. (2010).
Reliability of electromyographic methods used for assessing hip and knee
neuromuscular activity in females diagnosed with patellofemoral pain syndrome.
Journal of Electromyography and Kinesiology, 20, 142-7.
doi:10.1016/j.jelekin.2008.11.008
https://doi.org/10.1016/j.jelekin.2008.1...
; Briani
et al., 2015Briani, R.V., de Oliveira Silva, D., Pazzinatto, M.F., Albuquerque,
C.E., Ferrari, D., Aragão, F.A., & Azevedo, F.M. (2015). Comparison of frequency
and time domain electromyography parameters in women with patellofemoral pain.
Clinical Biomechanics, 30, 302-307.
doi:10.1016/j.clinbiomech.2014.12.014
https://doi.org/10.1016/j.clinbiomech.20...
; Uliam Kuriki
et al., 2011Uliam Kuriki, H., Mícolis de Azevedo, F., de Faria Negrão Filho, R.,
& Alves, N. (2011). Comparison of different analysis techniques for the
determination of muscle onset in individuals with patellofemoral pain syndrome.
Journal of Electromyography and Kinesiology : Official Journal of the International
Society of Electrophysiological Kinesiology, 21, 982-7.
doi:10.1016/j.jelekin.2011.08.002
https://doi.org/10.1016/j.jelekin.2011.0...
), its results are controversial and sometimes
the intraclass correlation coefficient (ICC) model chosen for the
reliability calculation does not allow the extrapolation of the results to the general
population. The comparison with respect to the reliability among these studies remains
quite difficult due to differences in experimental designs. Thus, a study evaluating the
reliability of EMG parameters in time and frequency domain during stair ascent and
descent, with a standardized experimental design, may shed some light on our
understanding about the more reliable gesture to analyze each variable.
The reliability is essential to all aspects of the measure, as it shows the quality of information and allows rational conclusions with regard the data (Weir, 2005Weir, J.P. (2005). Quantifying test-retest reliability using the intraclass correlation coefficient and the SEM. Journal of Strength and Conditioning Research., 19, 231-240.), therefore, the aim of this study was to determine the reliability of EMG parameters on the time and frequency domain, during stair ascent and descent in women with PFPS.
Methods
Thirty-one women with PFPS were recruited via advertisements placed at universities,
gyms and parks around the city. The sample size was calculated based on recommendations
of Walter, Eliasziw, & Donner, (1998)Walter, S.D., Eliasziw, M., & Donner, A. (1998). Sample Size and
Optimal Designs for Reliability Studies. Statistics in Medicine, 17, 101-110.
doi:10.1002/(SICI)1097-0258(19980115)17:1<101::AID-SIM727>3.0.CO;2-E
https://doi.org/10.1002/(SICI)1097-0258(...
using
alpha ≤ .05, p
0 = .56 and p
1 = .89, the lowest and the highest level of reliability were found in
previous studies, respectively (Bolgla et
al., 2010Bolgla, L.A, Malone, T.R., Umberger, B.R., & Uhl, T.L. (2010).
Reliability of electromyographic methods used for assessing hip and knee
neuromuscular activity in females diagnosed with patellofemoral pain syndrome.
Journal of Electromyography and Kinesiology, 20, 142-7.
doi:10.1016/j.jelekin.2008.11.008
https://doi.org/10.1016/j.jelekin.2008.1...
; Briani et
al., 2015Briani, R.V., de Oliveira Silva, D., Pazzinatto, M.F., Albuquerque,
C.E., Ferrari, D., Aragão, F.A., & Azevedo, F.M. (2015). Comparison of frequency
and time domain electromyography parameters in women with patellofemoral pain.
Clinical Biomechanics, 30, 302-307.
doi:10.1016/j.clinbiomech.2014.12.014
https://doi.org/10.1016/j.clinbiomech.20...
; Ferrari et
al., 2014Ferrari, D., Kuriki, H.U., Silva, C.R., Alves, N., & Mícolis de
Azevedo, F. (2014). Diagnostic Accuracy of the Electromyography Parameters Associated
With Anterior Knee Pain in the Diagnosis of Patellofemoral Pain Syndrome. Archives of
Physical Medicine and Rehabilitation, 95, 1521-6.
doi:10.1016/j.apmr.2014.03.028
https://doi.org/10.1016/j.apmr.2014.03.0...
). A minimum of 22 individuals was estimated to be needed
to ensure 80% power. All women were between 18 to 30 years. The study was approved by
the State University of West Paraná Human Ethics Committee (096/2013), and each
participant gave written informed consent prior to participation. The criteria used for
the diagnosis of PFPS were based on those used in other PFPS studies (Briani et al., 2015Briani, R.V., de Oliveira Silva, D., Pazzinatto, M.F., Albuquerque,
C.E., Ferrari, D., Aragão, F.A., & Azevedo, F.M. (2015). Comparison of frequency
and time domain electromyography parameters in women with patellofemoral pain.
Clinical Biomechanics, 30, 302-307.
doi:10.1016/j.clinbiomech.2014.12.014
https://doi.org/10.1016/j.clinbiomech.20...
; de Oliveira Silva et al., 2015De Oliveira Silva, D., Briani, R.V., Pazzinatto, M.F., Ferrari, D.,
Aragão, F.A., de Albuquerque, C.E., ... de Azevedo, F.M. (2015). Reliability and
differentiation capability of dynamic and static kinematic measurements of rearfoot
eversion in patellofemoral pain. Clinical Biomechanics, 30, 144-148.
doi:10.1016/j.clinbiomech.2014.12.009
https://doi.org/10.1016/j.clinbiomech.20...
;
Ferrari et al., 2014Ferrari, D., Kuriki, H.U., Silva, C.R., Alves, N., & Mícolis de
Azevedo, F. (2014). Diagnostic Accuracy of the Electromyography Parameters Associated
With Anterior Knee Pain in the Diagnosis of Patellofemoral Pain Syndrome. Archives of
Physical Medicine and Rehabilitation, 95, 1521-6.
doi:10.1016/j.apmr.2014.03.028
https://doi.org/10.1016/j.apmr.2014.03.0...
): (1)
anterior knee pain during at least 2 of the following activities: remaining seated,
squatting, kneeling, running, climbing stairs; (2) pain during patellar palpation; (3)
symptoms for at least 1 month with an insidious start; (4) pain level up to 3cm on a
10-cm VAS in the previous week; and (5) at least 3 positive clinical signs of the
following tests: Noble compression, McConnell, Waldron, Zohler's sign, Clarke's sign, Q
angle higher than 18º, and patella in the medial or lateral position. These criteria do
not indicate the severity of PFPS; they only classify as PFPS or not. The participants
needed to fulfill all 5 requirements to be included.
Any condition besides PFPS was considered an exclusion criterion, such as events of patellar subluxation or dislocation, lower limb inflammatory process, osteoarthritis, patellar tendon or meniscus tears, bursitis, ligament tears or the presence of neurological diseases. Those who had knee surgery and knee treatments such as arthroscopy, steroid injections, oral steroids, opiate treatment, acupuncture or physiotherapy during the previous 6 months were excluded from this study.
All the participants were evaluated according to the exclusion and inclusion criteria by two investigators with five years of clinical practice and were only allocated into the PFPS group if these two investigators were in agreement about the criteria.
Instrumentation
The experimental design included a stair designed according to Yu and colleagues (1997)Yu, B., Kienbacher, T., Growney, E.S., Johnson, M.E., & An, K.N.
(1997). Reproducibility of the kinematics and kinetics of the lower extremity during
normal stair-climbing. Journal of Orthopaedic Research, 15, 348-52.
doi:10.1002/jor.1100150306
https://doi.org/10.1002/jor.1100150306...
recommendations (Yu, Kienbacher, Growney, Johnson, & An, 1997Yu, B., Kienbacher, T., Growney, E.S., Johnson, M.E., & An, K.N.
(1997). Reproducibility of the kinematics and kinetics of the lower extremity during
normal stair-climbing. Journal of Orthopaedic Research, 15, 348-52.
doi:10.1002/jor.1100150306
https://doi.org/10.1002/jor.1100150306...
) with seven steps,
each step being 28cm deep, 18cm high and 1m width, with a 2m walkway in front of and at
the top of it. These dimensions are according to the Brazilian Regulatory Standards for
construction of stairs 9077/2001 (Brazilian Association of Technical Standards).
EMG data were collected using a conditioner module (Lynx(r), Sao Paulo, BRA; model 1000-8-4I) with a fourth-order, zero-lag, Butterworth digital filter with cutoff frequencies of 20 to 500Hz and an amplifier with a gain of 50. The preamplifier circuit on the electrode cable had a gain of 20, a common mode rejection ratio greater than 80dB, and an impedance of 1012Ω. The raw EMG signal was recorded at a sampling rate of 4000Hz. Two pairs of bipolar surface-capture Ag/AgCl electrodes (Kendall, Mansfield, MA, USA; model Medi-Trace) with diameters of 10mm were used to obtain VM and VL EMG data. The data were collected using AqdAnalysis software (Lynx(r), Sao Paulo, SP, BRA; model EMG 1000-8-4I). An electrostimulation device (Quark(r), Piracicaba, SP, BRA; model Nemesys 942) was used to find the VM and VL motor point in painful lower limb.
To ensure a natural stair climbing pattern, participants were not aware of the force plate (AMTI, OR6, Watertown, MA, USA) which was hidden within the fourth step; only the investigator knew of its existence and position, the force plate was mechanically coupled to the ground (i.e. independent and uncoupled from the stair structure). It was used to obtain ground reaction force data and, thus, to establish the moment when the subject was passing over the step. The force plate acquisition sampling rate was of 2000Hz.
Procedure
After finding the VM and VL motor point, the skin over the anterior portion of the thigh
was cleaned with rubbing alcohol. The electrodes were placed 2cm below the motor point
in the direction of the muscle belly, (Hermens, Freriks,
Disselhorst-Klug, & Rau, 2000Hermens, H.J., Freriks, B., Disselhorst-Klug, C., & Rau, G. (2000).
Development of recommendations for SEMG sensors and sensor placement procedures.
Journal of Electromyography and Kinesiology, 10, 361-374.
doi:10.1016/S1050-6411(00)00027-4
https://doi.org/10.1016/S1050-6411(00)00...
) with a 20mm interelectrode distance. This
motor point method for positioning the electrodes is in accordance with the Surface
Electromyography for the Non-Invasive Assessment of Muscles (SENIAM) (Uliam Kuriki et al., 2011Uliam Kuriki, H., Mícolis de Azevedo, F., de Faria Negrão Filho, R.,
& Alves, N. (2011). Comparison of different analysis techniques for the
determination of muscle onset in individuals with patellofemoral pain syndrome.
Journal of Electromyography and Kinesiology : Official Journal of the International
Society of Electrophysiological Kinesiology, 21, 982-7.
doi:10.1016/j.jelekin.2011.08.002
https://doi.org/10.1016/j.jelekin.2011.0...
). The
reference electrode was placed over the tibial tubercle.
The laboratory temperature and illumination were controlled. Before data collection, participants were familiarized with the protocol and, once they felt comfortable and the investigators deemed they were ascending and descending stairs with consistent velocity and proper performance, the sEMG data collection commenced.
Each participant was asked to ascent and descent the stairs at their natural comfortable
speed across the staircase and five successful trials were collected. The trial was
considered valid when the participant touches the force plate with the symptomatic lower
limb evaluated by EMG. As demonstrated by Jordan
et al, (2007)Jordan, K., Challis, J.H., & Newell, K.M. (2007). Walking speed
influences on gait cycle variability. Gait & Posture, 26, 128-34.
doi:10.1016/j.gaitpost.2006.08.010
https://doi.org/10.1016/j.gaitpost.2006....
(Jordan,
Challis, & Newell, 2007Jordan, K., Challis, J.H., & Newell, K.M. (2007). Walking speed
influences on gait cycle variability. Gait & Posture, 26, 128-34.
doi:10.1016/j.gaitpost.2006.08.010
https://doi.org/10.1016/j.gaitpost.2006....
) controlling the timing of the stair ascent and/or
descent can change the sEMG signal for gait in healthy subjects, thus, the speed of
stair ascent and descent was not controlled in this study. To ensure a natural stairs
negotiation pattern, participants were not made aware of the force plate, which was
hidden within the fourth step covered by a rubberized fabric, making it impossible to
distinguish the force plate from the other steps. For the reliability analysis, the
trials were performed in the same period of the day and in the same manner on 2 separate
days, with an interval of 2 to 7 days between the 2 collection periods. The subjects
were oriented to keep their daily life activities and routine physical activity between
the two days of collect data. Studies have shown that electrode positions may be the
cause of measurement variability (Smoliga, Myers,
Redfern, & Lephart, 2010Smoliga, J.M., Myers, J.B., Redfern, M.S., & Lephart, S.M. (2010).
Reliability and precision of EMG in leg, torso, and arm muscles during running.
Journal of Electromyography and Kinesiology : Official Journal of the International
Society of Electrophysiological Kinesiology, 20, e1-9.
doi:10.1016/j.jelekin.2009.09.002
https://doi.org/10.1016/j.jelekin.2009.0...
) and, as the collection of this study was
performed on 2 different days, a template using the participants' anatomic references
was developed (Ferrari et al.,
2014Ferrari, D., Kuriki, H.U., Silva, C.R., Alves, N., & Mícolis de
Azevedo, F. (2014). Diagnostic Accuracy of the Electromyography Parameters Associated
With Anterior Knee Pain in the Diagnosis of Patellofemoral Pain Syndrome. Archives of
Physical Medicine and Rehabilitation, 95, 1521-6.
doi:10.1016/j.apmr.2014.03.028
https://doi.org/10.1016/j.apmr.2014.03.0...
), furthermore, the electrodes were placed by the same person in both
days.
EMG analysis
The analyzed EMG signals were referenced by the vertical component of ground reaction force measured by the force plate. Therefore, the EMG signal was considered only while the participant was crossing the fourth step. The vertical component of ground reaction force being a marker of the beginning and the end of the EMG data collection. All processing was performed in MATLAB(r) (The MathWorks, Inc, Natick, MA).
The power spectrum density (PSD) is often used to analyze EMG frequency analysis (Silva, Silva, Ferrari, et al.,
2014Silva, C.R., Silva, D.O., Aragão, F.A., Ferrari, D., Alves, N., &
Azevedo, F.M. (2014). Influence of neuromuscular fatigue on co-contraction between
vastus medialis and vastus lateralis during isometric contractions. Kinesiology
(Zagreb), 46, 179-185.; Smoliga et al.,
2010Smoliga, J.M., Myers, J.B., Redfern, M.S., & Lephart, S.M. (2010).
Reliability and precision of EMG in leg, torso, and arm muscles during running.
Journal of Electromyography and Kinesiology : Official Journal of the International
Society of Electrophysiological Kinesiology, 20, e1-9.
doi:10.1016/j.jelekin.2009.09.002
https://doi.org/10.1016/j.jelekin.2009.0...
). The filtered EMG data time series was calculated using the fast Fourier
transform. From this calculation the median frequency (Fmed) was extracted, which is
when the integral of the left side of the spectrum is equal to that of the right side
(Solomonow et al., 1990Solomonow, M., Baten, C., Smit, J., Baratta, R., Hermens, H.,
D'Ambrosia, R., & Shoji, H. (1990). Electromyogram power spectra frequencies
associated with motor unit recruitment strategies. Journal of Applied Physiology, 68,
1177-85.).
The intensity of the PSD was normalized as follows: (1) calculation of the spectral
distribution function, which is the cumulative sum of the power spectrum divided by its
maximum value and multiplied by 100, and (2) calculation of the derived spectral
distribution function to obtain a PSD with intensity values normalized between 0 and
100. The mean intensity was calculated for each of the 3 frequency bands considered for
analysis from the normalized PSD: low (15-45Hz) (B1), medium (45-96Hz) (B2), and high
(96-400Hz) (B3) this bands were defined according to previous PFPS studies (Briani et al., 2015Briani, R.V., de Oliveira Silva, D., Pazzinatto, M.F., Albuquerque,
C.E., Ferrari, D., Aragão, F.A., & Azevedo, F.M. (2015). Comparison of frequency
and time domain electromyography parameters in women with patellofemoral pain.
Clinical Biomechanics, 30, 302-307.
doi:10.1016/j.clinbiomech.2014.12.014
https://doi.org/10.1016/j.clinbiomech.20...
; Ferrari et al., 2014Ferrari, D., Kuriki, H.U., Silva, C.R., Alves, N., & Mícolis de
Azevedo, F. (2014). Diagnostic Accuracy of the Electromyography Parameters Associated
With Anterior Knee Pain in the Diagnosis of Patellofemoral Pain Syndrome. Archives of
Physical Medicine and Rehabilitation, 95, 1521-6.
doi:10.1016/j.apmr.2014.03.028
https://doi.org/10.1016/j.apmr.2014.03.0...
).
In relation to EMG Onset analysis, automatic algorithm method was utilized. This
technique was suggested as the most prevalent onset techniques performed in muscular
contraction studies (Cavazzuti et al.,
2010Cavazzuti, L., Merlo, A., Orlandi, F., & Campanini, I. (2010).
Delayed onset of electromyographic activity of vastus medialis obliquus relative to
vastus lateralis in subjects with patellofemoral pain syndrome. Gait & Posture,
32, 290-5. doi:10.1016/j.gaitpost.2010.06.025
https://doi.org/10.1016/j.gaitpost.2010....
; Uliam Kuriki et al.,
2011Uliam Kuriki, H., Mícolis de Azevedo, F., de Faria Negrão Filho, R.,
& Alves, N. (2011). Comparison of different analysis techniques for the
determination of muscle onset in individuals with patellofemoral pain syndrome.
Journal of Electromyography and Kinesiology : Official Journal of the International
Society of Electrophysiological Kinesiology, 21, 982-7.
doi:10.1016/j.jelekin.2011.08.002
https://doi.org/10.1016/j.jelekin.2011.0...
; Williams, Haq, & Lee, 2013Williams, J.M., Haq, I., & Lee, R.Y. (2013). An investigation into
the onset, pattern, and effects of pain relief on lumbar extensor electromyography in
people with acute and chronic low back pain. Journal of Manipulative and
Physiological Therapeutics, 36, 91-100.
doi:10.1016/j.jmpt.2012.12.006
https://doi.org/10.1016/j.jmpt.2012.12.0...
).
Initially, a linear envelope was applied to the signal and data were full-wave rectified
and low-pass filtered at 50Hz.
Automatic Onset muscle contraction was quantified as more than three standard-deviations
of signal alteration for a minimum of 25ms above the baseline level of each muscle by
another algorithm (Bolgla et al.,
2010Bolgla, L.A, Malone, T.R., Umberger, B.R., & Uhl, T.L. (2010).
Reliability of electromyographic methods used for assessing hip and knee
neuromuscular activity in females diagnosed with patellofemoral pain syndrome.
Journal of Electromyography and Kinesiology, 20, 142-7.
doi:10.1016/j.jelekin.2008.11.008
https://doi.org/10.1016/j.jelekin.2008.1...
; Cowan, Bennell, Hodges, Crossley, &
McConnell, 2001Cowan, S.M., Bennell, K.L., Hodges, P.W., Crossley, K.M., &
McConnell, J. (2001). Delayed onset of electromyographic activity of vastus medialis
obliquus relative to vastus lateralis in subjects with patellofemoral pain syndrome.
Archives of Physical Medicine and Rehabilitation, 82, 183-9.
doi:10.1053/apmr.2001.19022
https://doi.org/10.1053/apmr.2001.19022...
; Kim & Song, 2012Kim, H., & Song, C.H. (2012). Comparison of the VMO/VL EMG Ratio and
Onset Timing of VMO Relative to VL in Subjects with and without Patellofemoral Pain
Syndrome. Journal of Physical Therapy Science, 24, 1315-1317.
doi:10.1589/jpts.24.1315
https://doi.org/10.1589/jpts.24.1315...
).
After identifying the respective values, an algorithm subtracted the VL onset from the
VM, where negative differences indicated previous activation of the VM and positive
differences indicated previous activation of the VL (Uliam Kuriki et al., 2011Uliam Kuriki, H., Mícolis de Azevedo, F., de Faria Negrão Filho, R.,
& Alves, N. (2011). Comparison of different analysis techniques for the
determination of muscle onset in individuals with patellofemoral pain syndrome.
Journal of Electromyography and Kinesiology : Official Journal of the International
Society of Electrophysiological Kinesiology, 21, 982-7.
doi:10.1016/j.jelekin.2011.08.002
https://doi.org/10.1016/j.jelekin.2011.0...
).
Statistical analysis
Statistical analysis was done using SPSS version 18 (SPSS Inc., Chicago IL). Descriptive
statistics for sample characteristics were expressed using mean ± standard deviation.
Intraclass correlation coefficient (ICC) (2,k) was used to express relative reliability
of the measures(Weir, 2005Weir, J.P. (2005). Quantifying test-retest reliability using the
intraclass correlation coefficient and the SEM. Journal of Strength and Conditioning
Research., 19, 231-240.). ICC expresses the
ratio of between-subject variance to within-subject variance and is a unitless value 24.
descriptors for reliability coefficients were used to describe the degree of
reliability: .00 to .25 - little, if any correlation; .26 to .49 - low correlation; .50
to .69 - moderate correlation; .70 to .89 - high correlation and .90 to 1.00 - very high
correlation (Kellis & Katis, 2008Kellis, E., & Katis, A. (2008). Reliability of EMG power-spectrum
and amplitude of the semitendinosus and biceps femoris muscles during ramp isometric
contractions. Journal of Electromyography and Kinesiology, 18, 351-8.
doi:10.1016/j.jelekin.2006.12.001
https://doi.org/10.1016/j.jelekin.2006.1...
; Mathur, Eng, & MacIntyre, 2005Mathur, S., Eng, J.J., & MacIntyre, D.L. (2005). Reliability of
surface EMG during sustained contractions of the quadriceps. Journal of
Electromyography and Kinesiology, 15, 102-10.
doi:10.1016/j.jelekin.2004.06.003
https://doi.org/10.1016/j.jelekin.2004.0...
). Standard error
of the measurement (SEM) was used to express absolute reliability of the measure (Silva, Silva, Aragão, et al., 2014Silva, C.R., Silva, D.O., Ferrari, D., Negrão Filho, R.F., Alves, N.,
& Azevedo, F.M. (2014). Exploratory study of electromyographic behavior of the
vastus medialis and vastus lateralis at neuromuscular fatigue onset. Motriz, 20,
213-220. doi:dx.doi.org/10.1590/S1980-65742014000200012
https://doi.org/10.1590/S1980-6574201400...
;
Weir, 2005Weir, J.P. (2005). Quantifying test-retest reliability using the
intraclass correlation coefficient and the SEM. Journal of Strength and Conditioning
Research., 19, 231-240.). SEM is calculated from the square
root of the error variance (i.e., mean of standard deviations from day 1 and day 2) and
has the same unit as the tested variable. In addition, SEM values were normalized by
mean to obtain their values on a 0 to 100 percentage scale. Smaller values of SEM
reflect more reliable measures (Weir, 2005Weir, J.P. (2005). Quantifying test-retest reliability using the
intraclass correlation coefficient and the SEM. Journal of Strength and Conditioning
Research., 19, 231-240.).
Results
All 31 volunteers have completed the two test days. The data related to the anthropometric measures and lower limbs evaluated are presented in Table 1.
The mean value, standard deviation, SEM and ICC of the variables in the time and frequency domain are described in Tables 2 and 3. The onset does not have to separate the VM and VL muscles values, because it is the delayed onset activation of these muscles. The results were separated according to the gestures of ascent (Table 2) and descent (Table 3).
Discussion
The stairs have been placed on experimental designs in order to reproduce a functional gesture. And, in the case of subjects with PFPS, it reproduces a gesture in which the symptoms are exacerbated. However, to date, it is not known if there are and which are the EMG differences between the gestures of ascent and descent stairs. Thus, the aim of this study is to determine the reliability of EMG parameters in these two gestures and report which one presents more reliable results.
Our sample follows the same profile used in studies with similar experimental design
(Bolgla et al., 2010Bolgla, L.A, Malone, T.R., Umberger, B.R., & Uhl, T.L. (2010).
Reliability of electromyographic methods used for assessing hip and knee
neuromuscular activity in females diagnosed with patellofemoral pain syndrome.
Journal of Electromyography and Kinesiology, 20, 142-7.
doi:10.1016/j.jelekin.2008.11.008
https://doi.org/10.1016/j.jelekin.2008.1...
; Ferrari et al., 2014Ferrari, D., Kuriki, H.U., Silva, C.R., Alves, N., & Mícolis de
Azevedo, F. (2014). Diagnostic Accuracy of the Electromyography Parameters Associated
With Anterior Knee Pain in the Diagnosis of Patellofemoral Pain Syndrome. Archives of
Physical Medicine and Rehabilitation, 95, 1521-6.
doi:10.1016/j.apmr.2014.03.028
https://doi.org/10.1016/j.apmr.2014.03.0...
; Kuriki et al., 2012Kuriki, H.U., De Azevedo, F.M., Filho, R. de F.N., & Alves, N.
(2012). Onset of quadriceps activation and torque variation during stair ascent in
individuals with patellofemoral pain. Conscientiae Saúde, 11, 642-650.
doi:10.5585/ConsSaude.v11n4.3810
https://doi.org/10.5585/ConsSaude.v11n4....
). Studies that
evaluated parameters in the frequency domain showed moderate to high reliability during
stair deambulation (Briani et al.,
2015Briani, R.V., de Oliveira Silva, D., Pazzinatto, M.F., Albuquerque,
C.E., Ferrari, D., Aragão, F.A., & Azevedo, F.M. (2015). Comparison of frequency
and time domain electromyography parameters in women with patellofemoral pain.
Clinical Biomechanics, 30, 302-307.
doi:10.1016/j.clinbiomech.2014.12.014
https://doi.org/10.1016/j.clinbiomech.20...
; Ferrari et al.,
2014Ferrari, D., Kuriki, H.U., Silva, C.R., Alves, N., & Mícolis de
Azevedo, F. (2014). Diagnostic Accuracy of the Electromyography Parameters Associated
With Anterior Knee Pain in the Diagnosis of Patellofemoral Pain Syndrome. Archives of
Physical Medicine and Rehabilitation, 95, 1521-6.
doi:10.1016/j.apmr.2014.03.028
https://doi.org/10.1016/j.apmr.2014.03.0...
), corroborating with our findings. The EMG frequency parameters
demonstrated to be an adequate diagnostic tool for PFPS (Ferrari et al., 2014Ferrari, D., Kuriki, H.U., Silva, C.R., Alves, N., & Mícolis de
Azevedo, F. (2014). Diagnostic Accuracy of the Electromyography Parameters Associated
With Anterior Knee Pain in the Diagnosis of Patellofemoral Pain Syndrome. Archives of
Physical Medicine and Rehabilitation, 95, 1521-6.
doi:10.1016/j.apmr.2014.03.028
https://doi.org/10.1016/j.apmr.2014.03.0...
). Therefore, this experimental design
can be implemented to diagnose individuals with PFPS (Yu
et al., 1997Yu, B., Kienbacher, T., Growney, E.S., Johnson, M.E., & An, K.N.
(1997). Reproducibility of the kinematics and kinetics of the lower extremity during
normal stair-climbing. Journal of Orthopaedic Research, 15, 348-52.
doi:10.1002/jor.1100150306
https://doi.org/10.1002/jor.1100150306...
).
The time domain parameters continue to be investigated, however, few researches have
shown the consistency of its measures. The null (-.17) and moderate (.59) reliability
during stair descent and ascent, respectively, with high SEM, for the parameters in the
time domain reveals that this variable is not consistent and the results are unreliable.
In contrast, a research developed with healthy young individuals, revealed very high
levels of reliability, being .96 on the descent and .91 on the ascent (Cowan et al., 2000Cowan, S.M., Bennell, K.L., & Hodges, P.W. (2000). The test-retest
reliability of the onset of concentric and eccentric vastus medialis obliquus and
vastus lateralis electromyographic activity in a stair stepping task. Physical
Therapy in Sport, 1, 129-136. doi:10.1054/ptsp.2000.0036
https://doi.org/10.1054/ptsp.2000.0036...
). Another study
obtained an ICC of 0.70 during stair descent in females with PFPS (Bolgla et al., 2010Bolgla, L.A, Malone, T.R., Umberger, B.R., & Uhl, T.L. (2010).
Reliability of electromyographic methods used for assessing hip and knee
neuromuscular activity in females diagnosed with patellofemoral pain syndrome.
Journal of Electromyography and Kinesiology, 20, 142-7.
doi:10.1016/j.jelekin.2008.11.008
https://doi.org/10.1016/j.jelekin.2008.1...
).
The main difference between these and our results is the statistical model used to calculate the reliability. The aforementioned research opted for the 3.5 ICC model, which should be performed when the goal is to analyze intra-rater reliability. In this case, it serves to establish the reliability of EMG equipment, exclusively used for the samples and cannot be generalized (Weir, 2005Weir, J.P. (2005). Quantifying test-retest reliability using the intraclass correlation coefficient and the SEM. Journal of Strength and Conditioning Research., 19, 231-240.). Our study has chosen the 2.5 ICC model which provides test-retest reliability, thus, it detects the consistency of the measurement performed by an EMG equipment and also can be extrapolated to other similar equipment (Weir, 2005Weir, J.P. (2005). Quantifying test-retest reliability using the intraclass correlation coefficient and the SEM. Journal of Strength and Conditioning Research., 19, 231-240.). Besides, 2.5 ICC model take into account systematic and random errors, whereas, 3.5 ICC model only gets random errors (Weir, 2005Weir, J.P. (2005). Quantifying test-retest reliability using the intraclass correlation coefficient and the SEM. Journal of Strength and Conditioning Research., 19, 231-240.).
In general, it has been seen a slight difference between the reliability of the
parameters on the frequency domain during ascent and descent stairs. This can be
explained by the change in the sequence of recruitment-derecruitment pattern of motor
units (Gonzalez-Izal, Cadore, & Izquierdo,
2014Gonzalez-Izal, M., Cadore, E.L., & Izquierdo, M. (2014). Muscle
conduction velocity, surface electromyography variables, and echo intensity during
concentric and eccentric fatigue. Muscle & Nerve, 49, 389-397.
doi:10.1002/mus.23926
https://doi.org/10.1002/mus.23926...
; Howell, Fuglevand, Walsh, &
Bigland-Ritchie, 1995Howell, J.N., Fuglevand, A.J., Walsh, M.L., & Bigland-Ritchie, B.
(1995). Motor Unit Activity During Isometric and Concentric-Eccentric Contractions of
the Human First Dorsal Interosseus Muscle. Journal of Neurophysiology, 74,
0-3.). During concentric contraction (stair ascent) the
recruitment of motor units occurs from the lower to the higher threshold level
stimulation. Firstly, the low-threshold units are deflagrated (fatigue resistant), and
with the overload increasing, the high-threshold units are recruited (low resistance to
fatigue) (Kallio et al., 2013Kallio, J., Søgaard, K., Avela, J., Komi, P.V, Selänne, H., &
Linnamo, V. (2013). Motor unit firing behaviour of soleus muscle in isometric and
dynamic contractions. PloS One, 8, e53425.
doi:10.1371/journal.pone.0053425
https://doi.org/10.1371/journal.pone.005...
).
However, during the eccentric contraction can occur activation of stretch receptors,
leading to an activation of some polysynaptic afferent pathways, although temporarily,
that may inhibit low-threshold motoneurons and excite high-threshold motoneurons,
leading to a different activation pattern (Howell
et al., 1995Howell, J.N., Fuglevand, A.J., Walsh, M.L., & Bigland-Ritchie, B.
(1995). Motor Unit Activity During Isometric and Concentric-Eccentric Contractions of
the Human First Dorsal Interosseus Muscle. Journal of Neurophysiology, 74,
0-3.; Nardone,
Romano, & Schieppati, 1989Nardone, A., Romano, C., & Schieppati, M. (1989). Selective
recruitment of high-threshold human motor units during voluntary isotonic lengthening
of active muscles. Journal of Physiology, 409, 451-471.). Furthermore, the concentric contractions show
higher EMG activation, since they require a greater number of active motor units to
generate the same force compared to eccentric contractions (Kallio et al., 2013Kallio, J., Søgaard, K., Avela, J., Komi, P.V, Selänne, H., &
Linnamo, V. (2013). Motor unit firing behaviour of soleus muscle in isometric and
dynamic contractions. PloS One, 8, e53425.
doi:10.1371/journal.pone.0053425
https://doi.org/10.1371/journal.pone.005...
; Yu, 2014Yu, J. (2014). Comparison of Lower Limb Muscle Activity during Eccentric
and Concentric Exercises in Runners with Achilles Tendinopathy. Journal of Physical
Therapy Science, 26, 1351-1353.).
Considering the results and the paucity of research addressing the quality of these
measures, we note that in the context of the variables in the frequency domain, either
in the ascent or in the descent stair, they are consistent for studying individuals with
PFPS. Consequently, it can be explored as assessment and diagnosis method to PFPS.
Nonetheless, it is necessary to show the results regarding reliability to show de
quality of the measurements. The gesture of ascent is better to determine the pattern of
muscle activation in subjects with PFPS and then compare it with asymptomatic subjects,
due to a specific order of recruitment (low to high threshold). Therefore, it allows
quantify strength physiologically (Silva Jr,
2013Silva Jr, R.A. (2013). Normalização EMG: considerações da literatura
para avaliação da função muscular (EMG normalization: considerations from literature
to assess the muscle function). Conscientiae Saúde, 12, 470-479.
doi:10.5585/ConsSaude.v12n3.4362
https://doi.org/10.5585/ConsSaude.v12n3....
) and clearly determine other parameters such as Fmed, for example. On the
other hand, stair descent is indicated to check the activity of the quadriceps as a
result of higher demands muscle and mechanical compared to concentric activities,
besides being associated with higher rates of pain and joint stress (Powers, 2010Powers, C.M. (2010). The influence of abnormal hip mechanics on knee
injury: a biomechanical perspective. The Journal of Orthopaedic and Sports Physical
Therapy, 40, 42-51. doi:10.2519/jospt.2010.3337
https://doi.org/10.2519/jospt.2010.3337...
). In contrast, the results for the
delay in onset proved to be inconsistent and, therefore, should be cautious at the time
of extracting the information pertaining to these measures due to its high rates of
error.
There are some limitations of the present study that must be acknowledged. Firstly, the sample included only women. Although this subgroup is important to study, as these individuals are the most likely to be committed for PFPS, the results may not be generalizable to the entire population of people with PFPS. Secondly, the speed during stair deambulation was not controlled in any day, which does not allow to determine the speed influence on the EMG signal. Therefore, future studies should include men and to control factors that can influence the EMG, such as speed during stair deambulation.
Stair ascent has shown EMG characteristics more standard than stair descent. Moreover, it has exhibit moderate to high values of reliability in the frequency domain EMG parameters. Therefore, our results suggest that stair ascent and frequency domain EMG parameters are more reliable to evaluate EMG signals of subjects with PFPS in the most cases.
References
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Marcella Ferraz Pazzinatto, Danilo de Oliveira Silva, and Fábio Mícolis de Azevedo are affiliated with the São Paulo State University (Universidade Estadual Paulista), School of Science and Technology, Physical Therapy Department, Presidente Prudente, Brazil.
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Ronaldo Valdir Briani, Fernando Amâncio Aragão, and Carlos Eduardo de Albuquerque are affiliated with the State University of West Parana (Universidade Estadual do Oeste do Paraná), Physical Therapy Department, Cascavel-PR, Brazil.
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Deisi Ferrari is affiliated with the Bioengineering Postgraduate Program, São Carlos School of Engineering, University of São Paulo (Universidade de São Paulo), São Carlos, SP, Brazil.
Publication Dates
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Publication in this collection
Apr-Jun 2015
History
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Received
05 Feb 2015 -
Accepted
25 Mar 2015